1. Field of the Invention
The present invention relates to a high definition television (HDTV) receiver and, more particularly, to a HDTV receiver that is also capable of receiving NTSC signals.
The instant application is based on Korean Patent Application No. 94-37542, which is incorporated herein by reference for all purposes.
2. Brief Discussion of Related Art
Recently, the United States has elected the 8-VSB (Vestigial Side Band) modulation method as the designated method for HDTV transmission. It will be noted that HDTV broadcasting is initially planned to be put into service together with a conventional NTSC broadcasting. Thus, the HDTV receiver will be required to have a function capable of receiving both HDTV signals and conventional NTSC signals.
A dual-mode receiver for receiving HDTV signals and NTSC signals has been developed which is capable of processing the received signals by a HDTV or NTSC method according to a user""s selection. One such receiver, which is disclosed in U.S. Pat. No. 5,283,653 entitled xe2x80x9cDUAL HDTV/NTSC RECEIVER USING SEQUENTIALLY SYNTHESIZED HDTV AND NTSC CO-CHANNEL CARRIER FREQUENCIESxe2x80x9d to Citta (Feb. 1, 1994) includes a dual HDTV/NTSC television receiver able to automatically select an appropriate signal when tuned to a selected television channel. This receiver selectively receives HDTV and NTSC television signals in one channel, among a plurality of channels, in which HDTV signals are of an inherently lower power than the co-channel NTSC signals. A tuner in the receiver initially synthesizes a carrier frequency associated with the HDTV signal of the selected channel, and a narrow band sync detector detects the HDTV signal using the synthesized HDTV carrier frequency. A microprocessor enables further processing of either the HDTV signal or the NTSC according to the detection result of the HDTV signal.
The present invention was motivated by a desire to provide an improved HDTV/NTSC receiver while avoiding the problems inherent in the conventional receiver discussed above.
An object of the present invention is to provide a novel HDTV/NTSC receiver using symbol timing recovery and a sync signal detection.
Another object of the present invention is to provide a method of receiving both HDTV signals and NTSC signals using symbol timing recovery and sync signal detection.
These and other objects, features and advantages according to the present invention are provided by a receiver for selectively receiving HDTV television signals and NTSC television signals in a plurality of television channels. Preferably, the receiver includes:
a tuning unit for converting a desired one of HDTV signals and NTSC signals into an intermediate frequency signal;
a sync detector, coupled to receive the intermediate frequency signal output from the tuning unit, for detecting a sync signal of the NTSC signal;
a timing recovery unit, coupled to receive the intermediate frequency signal output from the tuning unit, for self-recovering symbol timing of the applied HDTV signal, and outputting a symbol timing lock signal and an analog-to-digital converted HDTV signal;
a controller for judging whether the currently received television signal is either a NTSC signal or a HDTV signal based on the sync detection result of the sync detector and the symbol timing lock signal from the timing recovery unit, and for outputting a control signal according to the determination result; and
a tuning controller for initially controlling the tuning unit so that one desired HDTV signal is received, and for subsequently controlling the tuning unit on the basis of the signal selected by the control signal among respective signals output from the tuning unit and the timing recovery unit.
These and other objects, features and advantages according to the present invention are provided by a method of receiving a signal of a desired channel in HDTV/NTSC television receiver. Advantageously, the method includes steps for:
(a) initially tuning a receiving signal to accept an HDTV signal of a desired channel and converting the tuned signal into an intermediate frequency signal;
(b) performing a self-recovery operation of symbol timing using the intermediate frequency signal generated during step (a) and generating a signal indicating a respective self-recovery result;
(c) tuning a receiving signal to accept a NTSC signal of the desired channel and converting the tuned signal into an intermediate frequency signal, if self-recovery operation of symbol timing is not accomplished during step (b);
(d) carrying out detection of the horizontal/vertical sync signal of the NTSC signal using the intermediate frequency signal generated in step (c), and providing a signal indicative of a detection result; and
(e) continuously receiving the HDTV signal when the self-recovery result signal indicates that symbol timing is self-recovered, and continuously receiving the NTSC signal when the detection result signal indicates that the horizontal/vertical sync signal is detected.
These and other objects, features and advantages of the invention are disclosed in or will be apparent from the following description of preferred embodiments.